The present invention relates to an apparatus for the examination of a body of living tissues. In particular, the present invention relates to an apparatus for telediaphanographic and ultrasonic investigation for use in the detection and diagnosis of cancer, and particularly breast cancer in women. The present invention further relates to an apparatus for imaging a body of living tissues.
It is now widely recognised that repeated use of X-ray mammography is valuable in the detection of breast cancer for women over 50 years but that in younger women aged less than 50 years where no benefits have been demonstrated the risk/benefit ratio is negative. In addition, in the young (&lt;50 years) dense breast X-ray mammography misses a significant proportion of cancers and other tumours when used as a diagnostic technique. It is thus widely recognised that for screening and for diagnosis new, preferably more accurate and risk free techniques are desirable to detect breast cancer at an early stage before the disease is disseminated to other organs. The Forrest Report published in the United Kingdom in 1987 recommends screening at 3 yearly intervals by X-ray mammography of women over 50 years. The interval is chosen to minimise economic costs and to limit cumulative X-ray dose to breast tissues as it has been reported that X-rays can themselves cause cancer and that the breast is an especially sensitive organ.
GB-A-2092856, GB-A-2111794, U.S. Pat. No. 4,600,011 and EP-A-0108617 (each of which are in the name of the present applicant and the disclosures of which are incorporated herein by reference) relate to optical methods of detecting breast cancer (and other cancers) using optical (non-ionising) radiation but even these methods have only shown sensitivity of about 0.9 for palpable lesions. In other words about 10% of tumours are missed or wrongly interpreted.
It is also known to attempt to detect breast cancer by using Doppler ultrasound techniques. Two documents which disclose such techniques are "The Scattering of Ultrasound by Blood Flowing in Tumours" by P.N. Burns, PhD. Thesis, University of Bristol, 1985 and "Tumour Detection by Ultrasonic Blood Flow Signals" by P.N.T. Wells et al, (1977) Ultrasonics (15); p. 231-232. Such methods detect blood flow changes at the advancing front of breast carcinoma. The signals from the associated volume of neovascularization differ from those obtained when normal tissues are interrogated. The flow velocity and the quantity of blood flowing are generally higher near a malignant tumor. The ultrasound Doppler data is normally presented in an isometric display and comparison made of the signals close to and far away from the suspected tumour. When Doppler ultrasound is used by itself as a breast screening technique every cubic centimetre of tissue must be separately interrogated and analysed. With a single transducer (of area typically 1 cm.sup.2) the method is very time consuming and required considerable computer memory, (typically more than provided by a microcomputer), to generate the isometric displays.